Fuel and method of making same



Patented Jan. 14, 1930 P TENT OFFICE ROBERT WILI-IELM STREHLENERT, or NOL, SWEDEN FUEL AND METHOD OF MAKING SAME No Drawing. Application filed .Tune 16, 1927, Serial No. 199,399, and. in Sweden May 18, 1926.

The present invention relates to a method the purpose of which is to manufacture fuel in an economical way from two different kinds of waste products obtained in two dif ferent branches of industry and each of which is considered as rather onerous. The waste products that are here in question are on the one hand those obtained in saw-mills and invention.

Saw-dusthas been burnt in the saw-mills or other works with rather uneconomical re sult, principally more for the removal or destruction of the same than for utilizing the low heat energy content of it. Attempts have also been made to make fuel briquets of saw-dust, but such attempts have as yet met without success in manufacturing such briquets of sufficient strength.

With regard to the sulphite liquor it is known that it can be decomposed to form a socalled sulphite fuel whereby, however, only about according to hitherto known methods, are recovered. It is known also to use sulphite liquor as a. liquid fuel. Cornpared with market prices of coal the price of sulphite fuel will be rather high, and the use of the sulphite liquor as a liquid fuel does not give-a result economical enoughfor an extensive use.

It is also known to use thesulphite liquor as a binding material in making briquets of coal-dust or brown coal-dust and in the manufacture of building materials for different 45- purposes. As an example of this may be cited such methods as are described for instance in Swedish Patents Nos. 14364. and 45359.

By the present invention it is possible to prepare a suitable material from said two waste products by a method by means of which there is obtained a satisfactory fuel as respects economy and whereby all the sul stancein the liquor that can be solidified is utilized. According to this method the sawdust is preferably dried to complete dryness. The sulphite liquor which is to be mixed with and fully absorbed by the saw-dust, is in any known manner evaporated to a concentration of 25 to about 60% dry substance, or the sulphite liquor may also be added successively to the saw-dust in which case the water in the liquor iseva-porated while mixing the substances. These two substances are mixed in an ordinary mixing apparatus, which takes only a very small amount of power. I have found that when the sulphite liquor is "absorbed by the fibrous Wood substance the salt in the liquor remains in the wood cells, while the water in which the salt has been dissolved escapes through the cellular tissue of the fibrous wood substance. The quantity of dry substance contained in the finished dry product and derived from the liquor may vary and may be 25 to 60% of the finished mass. A mixture containing about. equal parts of the both substances in the finished product gives, however, a very advantageous result. The mixing operation will be best done if the mass then contains about 36% Water. If sulphite liquor of higher or lower concentration is used it is better to keep the amount of water in the mixture momentary. In a. case like this such a binding cannot, however, take place under other conditions than those under which the mixture is dried to about nearly the limitof dryness. Even in such a case the liquor does not bindthe s aw-dust particles sufliciently together if the mass just before the pressing operation has not been steamed whereby the same is softened, and nor is it possible to obtain a briquet of suflicient density to sustain a certain pressure unless a steamed mass is employed.

A mass with said consistency cannot, however, be treated with steam in the same way as in ordinary steaming, that is to say, by blowing steam into the mass as such, as a uniform moistening would thereby not be obtained and the liquor furthermore would disengage from the saw-dust and the entire mass would be of a pasty consistency. For this reason the mass must according to this invention be steamed in the following manner. The mixture of liquor and saw-dust after having been dried so as to contain only a few percent of moisture is during its transport to the briquet press precipitated into a chamber, for instance a drum, a pipe conduit or the like, of suitable depth and into which at the bottom thereof is blown saturated steam. The short time that it takes the mass to pass said chamber on its way to the briquet press is, however, suflicient for a partial condensation of the steam upon the particles of the mixture and also suflicient for the necessary heating of the same. The mass takes up only about 2% of water, but this is sufficient in order to soften the liquor in such a degree that, when the mass arrives to the briquet press, it is in a condition to be compressed and at once may be pressed as a homogenous briquet so that the same does not later expand a or crack. The pressing of the briquets is performed in warm matrices.

The quantity of li uor residue contained in the briquets has first y the purpose of raising the value of the briquet as a fuel, and besides it increases its density and serves also as a binding material between the particles of the saw-dust and furthermore it makes the briquets unaffected by changes in atmo' sphericconditions, if the briquettes after having left the press are subjected to a drying carbonizing process at about 20090., the liquor residue is changed into an insoluble composition which in addition to conserved binding power still more increases the calorific power of the briquets.

Briquets manufactured in accordance with the method above described and at a pressure of about 600 kg. per Cm have a density between L4 and 1.5 which is about the weight of coal. Having left the press the briquetsother words the heat of reaction is sufiiificient for the carbonization process when the proportion between dry liquor and saw-dust is as above specified. This carbonization process is thus not to be confounded with before known carbonization processes for briquets and the like, as in a carbonization process where the percentage of liquor constitutes such a great part, as above specified, for carrying out the method in question, the dry liquor is in the first place acting as an introducer and then as a source of heat for the carbonizationprocess.

Instead of manufacturing briquets of the mass of liquor and saw-dust as'prepared' for this purpose said mass may also be used for the manufacture of a pulverous fuel.

It is well known that pulverous fuels ema nating from a solid product of a more or less valuable calorific content if being injected in the fire place give a considerably higher effect, and this effect will be higher the more the material is finely divided.v

Of course the briquets manufactured according to this invention may like other solid fuel be crushed to a pulverous fuel of which product results a technical effect that is proportionate to the degree of fineness of the particles, but such a process is always rather expensive.

.The material of which briquets are manufactured as above described may also, if desired, according to this invention be used for the manufacture of a pulverous fuel. The costs for carrying out the method for manufacturing such fuel are less than the costs for manufacturing the briquets. The method of manufacturing the pulverous fuel consists therein that the mass of sulphite liquor and saw-dust without being steamed is subjected to the same process as the briquets, when these are heated to 200 C. when all the liquor product in the mass at the sametime is transformed into an insoluble state.

As above indicated, an exothermic reac tion takes place during the said heating process acting in such a way upon the wood sub-' stance in the mass that this latter will loose its structure and be broken up in an amorphous powder or so changed in its nature, that the mass when subjected to some slight mechanical action will fall asunder in an amorphous powder. I I

The powder thus obtained is not to be confused with a crushed product which always has to be estimated by the size of the particles. The amorphous powder obtained according to this invention is formed during the course of the chemical reaction which takes place during the decomposition of the liquor product and the action upon the wood substance.

An amorphous mass thus produced and emanating from the constituent parts of the wood, lignin and cellulose, burns when injected in a fire place, and especially if preheated air then is used, like a combustible gas or oil and is of a thermal efiiciency which is quite comparable with the efliciency of these last named materials.

It is evident that the fuel in the amorphous state cannot be used anywhere and in all different places but is to be used when convenient. The briquets, which have a high weight of volume and thus are easy to transport, have their special market.

For the manufacture of one ton raw briquets or one ton amorphous powder there is required 580 kg. dry saw-dust and 4200 kg. ordinary waste sulphite liquor containing about 10% dry substance or a corresponding greater or less quantity of liquor depending upon the degree of dry substance contained in the same.

It is evident that instead of saw-dust there may be used finely divided wood obtained in any other way than by sawing.

Briquets in accordance with this invention may be manufactured at a price of about half the present price of coal and the amorphous powder at a price that is still considerably lower.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. The process of preparing a fuel from waste sulphite liquor and sawdust which comprises mlxing sawdust with a waste sulphite liquor in such concentration and proportion that the mixture on a dry basis contains about 25 to 60% dry materials derived from the sulphite liquor, partly drying the resulting mixture, heating the partly dried mixture with live steam to raise the temperature of the mixture and to moisten the mixture, forming the moistened mixture into briquettes under pressure and thereafter drying and heating the briquettes at a temperature not substantially in excess of 200 C.

2. In the process of preparing a fuel from waste sulphite liquor and sawdust, the steps which comprise heating to about 200 C. a dried mixture prepared by mixing sawdust with a sulphite liquor in such concentration and amount that the mixture on a dry basis contains about 25 to 60% of dry materials derived from the sulphite liquor.

3. A fuel consisting of a baked mixture of A sawdust and dried sulfite liquor the latter forming 25% to 60% of the mixture.

4:. A briquet consisting of a baked mixture of sawdust and dried waste sulfite liquor, the

latter ingredient forming 25% to 60% of the mixture.

5. A fuel consisting of a baked mixture of sawdust and dried sulfite liquor, the latterforming 25% to 60% of the mixture, said mixture being in an amorphous state.

6. In the process of preparing a fuel from waste sulfite liquor and sawdust, the steps hand.

ROBERT W. STREHLENERT. 

